gribplayground/README.md

GRIB Playground — Arctic Waves (no pygrib)

Overview

• Fetches NOAA GFSWave Arctic 9km GRIB2 and extracts wave height, direction, and period without pygrib.
• Uses xarray+cfgrib (ECCODES backend) to decode GRIB.

Requirements

• Python 3.9+
• Packages: xarray, cfgrib, eccodes, numpy, requests
• System: ecCodes installed (provides GRIB decoding used by cfgrib)

Install

• macOS (Homebrew): brew install eccodes
• Python deps: pip install xarray cfgrib eccodes numpy requests

Usage

• Download and summarize a specific forecast hour: python arctic_fetch.py --fh 6

• Specify date/run explicitly: python arctic_fetch.py --date 20250115 --run 12 --fh 18

Outputs

• Writes the downloaded GRIB to a temp file by default.
• Prints summary stats and a small JSON sample to stdout.
• Optional: --out-json /path/out.json to save sampled points.

Notes

• This script avoids pygrib and relies on cfgrib (ecCodes).
• If you need NetCDF output, add --out-nc /path/out.nc and uncomment the indicated line to save ds.to_netcdf.